The present invention relates to the general field of turbine engine combustion chambers. The invention relates more particularly to an annular wall for a forward-flow or a reverse-flow combustion chamber that is cooled by a “multi-perforation” method.
Typically, an annular turbine engine combustion chamber is made up of an inner annular wall (also referred to as an inner shroud) and an outer annular wall (also referred to as an outer shroud) that are connected together upstream by a transverse wall forming the chamber end wall.
Each of the inner and outer shrouds is provided with a plurality of various kinds of air admission holes and orifices enabling the air that flows around the combustion chamber to penetrate into the inside of the combustion chamber.
Thus, so-called “primary” and “dilution” holes are formed in these shrouds to convey air to the inside of the combustion chamber. The air passing through the primary holes contributes to creating an air/fuel mixture that is burnt in the chamber, while the air coming from the dilution holes is for enhancing the dilution of that air/fuel mixture.
The inner and outer shrouds are subjected to the high temperatures of the gas resulting from combustion of the air/fuel mixture.
For cooling purposes, additional “multi-perforation” orifices are also made through those shrouds over their entire surface area. These multi-perforation orifices are generally inclined at 60° and they enable the air flowing outside the chamber to penetrate into the inside of the chamber so as to form films of cooling air along the shrouds.
Nevertheless, in practice, it is found that the zones of the inner and outer shrouds that are situated around, and in particular directly downstream from, each of the primary or dilution holes present an absence of orifices as a result of the laser drilling technology used, and that they therefore benefit from a low level of cooling only, which implies that they suffer a risk of cracks forming and propagating.
In order to solve that problem, the Applicant has made proposals in its application FR 2 982 008 to provide additional cooling orifices immediately downstream from the primary holes or the dilution holes, the additional cooling orifices being arranged in a plane perpendicular to the flow direction of the combustion gas.
Nevertheless, although those additional orifices, which are said to be gyratory (because they are at 90°), do indeed deliver cooling that is effective compared with conventional axial multi-perforation for which the air film is stopped by the presence of those holes, they still suffer from certain drawbacks, in particular as a result of being fed solely by the static pressure of the air flowing around the combustion chamber.